All these squats look fairly decent, but there may be more things going on I'm just not seeing. So will definitely need to see the standard rear 45 degree angle before commenting. Its a lot easier to see knee/hip/back angle and what needs adjusting

Ryan -- I know these videos below of our squatsaren't at optimal angle either, but I didn't want to turn around and face the mirror. Result is more of a side view, albeit ~15 degrees back. Hopefully it is good enough to give you a better sense of our techniques:

me - 345x5 -- I think my first two reps are pretty good. But then I let myself get out over my toes on rep three. Lost some back tightness in last two reps.

son - 315x5 -- Still rushing some of his reps. Rep two he came up through his chest a bit. Last two reps have his hips shooting backward initially instead of up.

Although it is blocked by the rack, it does seem like you are not staying in low back extension. Keep the arch there just like the squeeze in the DL. Your son can synchronize the hips and knees better. His hips are going back first, then the knees. Make them bend at the same time